Improvements related to save of config file by LightningCLI

[mauvilsa]

What does this PR do?

A couple of improvements related to save of config file by LightningCLI.

• Exclude SaveConfigCallback for fast_dev_run != False.
• SaveConfigCallback give a clearer message if config file already exists.

Fixes #7859

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[pep8speaks]

Hello @mauvilsa! Thanks for updating this PR.

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2021-06-14 18:04:13 UTC

[codecov]

Codecov Report

Merging #7963 (6b4ac01) into master (cca0e75) will decrease coverage by 5%.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master   #7963    +/-   ##
=======================================
- Coverage      92%     87%    -5%     
=======================================
  Files         203     203            
  Lines       13127   13153    +26     
=======================================
- Hits        12013   11409   -604     
- Misses       1114    1744   +630     

[awaelchli]

great!